What’s Vulnerable › Vulnerabilities

CVE-2021-21265: October CMS vulnerable to Potential Host Header Poisoning on misconfigured servers

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-03-10 · updated 2026-06-17
• Weakness: CWE-644

Description

October is a free, open-source, self-hosted CMS platform based on the Laravel PHP Framework. In October before version 1.1.2, when running on poorly configured servers (i.e. the server routes any request, regardless of the HOST header to an October CMS instance) the potential exists for Host Header Poisoning attacks to succeed. This has been addressed in version 1.1.2 by adding a feature to allow a set of trusted hosts to be specified in the application. As a workaround one may set the configuration setting cms.linkPolicy to force.

Affected products

• octobercms october: before 1.1.2 — fixed in 1.1.2

How to fix

Upgrade to a fixed version: octobercms october 1.1.2. Check the vendor advisory for mitigations.

References

• https://github.com/octobercms/library/commit/f29865ae3db7a03be7c49294cd93980ec457f10d
• https://github.com/octobercms/library/commit/f86fcbcd066d6f8b939e8fe897409d152b11c3c6
• https://github.com/octobercms/october/commit/555ab61f2313f45d7d5d138656420ead536c5d30
• https://github.com/octobercms/october/commit/f638d3f78cfe91d7f6658820f9d5e424306a3db0
• https://github.com/octobercms/october/security/advisories/GHSA-xhfx-hgmf-v6vp
• https://packagist.org/packages/october/backend
• https://github.com/octobercms/library/commit/f86fcbcd066d6f8b939e8fe897409d152b11c3c6
• https://github.com/octobercms/october/commit/f638d3f78cfe91d7f6658820f9d5e424306a3db0
• https://github.com/octobercms/october/security/advisories/GHSA-xhfx-hgmf-v6vp

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